Home air conditioning systems generally divide the condenser and compressor functions because the home structure usually has a pitched roof. Further, the homeowner would not accept roof placement for asethetic reasons.
Commercial buildings, in contrast, usually have flat roofs, upon which an air conductor unit may be conveniently mounted. The commercial units include fresh air intake and recirculation intake provisions with both compressor and condenser functions in the same unit.
The unit is generally installed by building a frame, known in the trade as a "curb", to mount the unit above the roof line. The curb mounts the unit above water level on the roof.
The curb is placed around a roof opening and weather sealed by the roofer. Ducts are extended through the curb to the air conditioning unit for tempered air delivery and room air return. Comfort air conditioning had its first major use in motion picture theaters during the early 1920's. Motion picture theaters were among the first to adopt this new technology and by the late 1920's several hundred theaters throughout the country had been air conditioned. These were custom-designed, custom-manufactured, field-installed systems, which meant most of the assembly and erection of components was done on the job site.
The first self-contained room air conditioning systems began to appear toward the end of the 1920 decade. At that time the industry first attempted to package products that could be manufactured in mass production and factory tested prior to shipment to the ultimate user.
From that time on, rapid development took place in new and better refrigerants, precharged lines, and the refinement of heat pumps. The final major product innovation that occurred during the late 1950's and early 1960's and still accounts for the most dramatic growth rate of all packaged year-round conditioners is the rooftop conbination of heating and cooling units. This development started with small two to five ton systems being installed on the rooftops of low-rise commercial structures as well as some residential applications. At the present time capacities range upwards of 100 tons of cooling. Both gas and electricity are available for heating.
However, perfection has not been achieved in all respects. The roof installations currently available generally require considerable skilled labor on-site custom fitting. Prepackaged units, although self-contained, are necessarily fitted with some means of ducting the conditioned air through the roof into the structure, and receiving back room air for reconditioning. One of the common means of accomplishing this type of installation is to mount the prepackaged unit on elevated stilts of structural iron to keep the unit above the flood level on the roof structure. The duct work is then run through openings in the roof which are sealed by various roofing techniques, some of which are successful.
From this early beginning, there has been developed the concept of using a curb structure, which is essentially a dyked opening. The dyke prevents the entrance of water into the building and simultaneously supports the conditioning unit above the flood level on the roof. The roof curb varies for different manufacturers but essentially is constructed as shown in FIGS. 5 and 6 of the drawings. FIGS. 5 and 6 are supplied in order to enable a clear understanding of the contrast of this invention to the prior art and the purpose for the contrast.
In FIG. 6, a roof supporting beam 110 of the building supports conventional roof deck 114. It is common practice to use insulation 115 directly over metal roof decking. Then, the roofing material, such as felt and built-up roofing, is added to waterproof the roof.
The conventional structure employs a rigid, galvanized steel base 116 which is, in effect, a four-sided dyke attached to the roof joist prior to the roof installation. Rigid foam insulation 117 is conventionally placed on the surface of the base dyke in order to prevent moisture condensation. A cant strip 118 is used to form a fillet for the roofing material in order to prevent cracking of the material in a sharp corner.
The prior art practice is illustrated in the provision of a wood nailing strip 119 in FIG. 6. The strip 119 is positioned on top of the side wall of base 116 and therefore requires, in this type of installation, an onsite skilled workman. Furthermore, the placement of the nailing strip requires the base side wall to support the nailing strip. The present invention reverses that function, as will be explained in more detail.
The roofing material is extended up over the insulation 117 and nailed to the strip 119 for a solid anchor. Outer flashing 120 is then extended down over the nailing strip and roofing material to shield the joint ending of the roofing against blowing water leaks.
In this prior conventional structure, a further upright annular insulation wall 121 is secured to the top of the base 116. Then, the unit 122, containing the factory assembled air conditioning equipment, is placed on top of the curb. It is common practice to provide such unit with a base channel 123 and to use an indexing pin 124 to locate the unit by means of an indexing opening in the base channel 123.
The unit 122 is provided with a soft, flexible insulation channel 124 which fits down upon the annular wall 121 and forms an air lock seal. It is generally not necessary to bolt the unit 122 upon the curb but rather to let it sit over the guide pin and partially supported by compression of the flexible insulation material.
After the unit is seated in place upon the structure thus described, duct work must be secured into suitable openings in the bottom of the factory supplied unit. FIG. 5 of the drawings represents an oversimplified cross-section of the components of a unit 122. A return air duct is extended up through the opening outlined by the curb base 116 and attached to the unit. Return air is directed over filters 126 and through the cooling coil 125 by a circulation fan 128. The air is then forced through the heat exchanger and out through a supply duct to the conditioned space.
FIG. 5 emphasizes the prior art method for the connection of duct work 27 to the unit to receive and distribute the conditioned air. In most installations only a single outlet is provided and distribution must be done by custom metal work within the building itself. By contrast, the present invention employs the curb as a distribution chamber or plenum as well as for support of the unit, as will be further explained.
Such prior construction requires considerable skilled installation labor in that the fitting of the ducts to the units is custom work requiring skilled personnel.
Inherent in custom installation is delay. The logistics of tradesmen supply is a known frustration to speedy construction.
Further, weather sealing has been known to present severe problems. The curb is usually metal. The roofing material sticks well to metal when fresh, but soon loses elasticity and then cracks develop to allow water leaks.
Therefore it is an object of this invention to provide an apparatus which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the air conditioning installation art.
It is another object of this invention to provide a factory built curb requiring little on-site skilled labor.
A further object is to enable a positive attachment of roofing to the curb to prevent water leaks.
It is also a primary object to enable better plenum distribution of the tempered air by means of a chamber area separate from the air conditioning unit.
A further object is to provide for return air through the curb chamber in order to avoid on-site establishment of this function.
Yet another object is to provide a fully factory built curb but tailored to specific installation requirements.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.